Abstract

Raniganj field in West Bengal is the largest producing coal bed methane reservoir in India, belonging to the Gondwana Super Group. Block RG (East)-CBM-2001/1 is located in the eastern-most part of Raniganj coalfield. The block was awarded to Essar Oil Limited under the CBM Round I of the Government of India in 1997. More than 1200 hydraulic fracturing jobs have been carried out since then. Fracturing treatment plans for each well in this block comprises of more than one hydraulic fracturing job since this coal-bed reservoir is made up of a number of laminated sequences of coal seams separated at variable distances. Due to a very strong heterogeneity between these seams, it is essential to understand the behavior of fracture propagation in all of them individually.

Fracture diagnostics involves analyzing the data before, during, and after a hydraulic fracture treatment to determine the shape and dimensions of both the created and propped fracture. Fracture diagnostic techniques can provide important data when entering a new area or a new formation. In most cases, however, fracture diagnostics is expensive, which limits its widespread use in industry. However, many researchers have come up with a much simpler and cost effective technique of predicting the fracture behavior based on the analysis of net pressure trend of the fracturing job. Analysis of fracturing treatment pressure behavior is an easy tool to gain some insight into the fracturing parameters and fracture propagation, and consequently, optimize the future fracturing treatments.

The ever exhaustive fracturing database of Essar Oil Limited was taken into deliberation to study the fracturing treatments carried out in different seams and an attempt is made to correlate the efficacy of these treatments based on the diagnostic tools postulated by Nolte (1979) and Conway (1985). The study is been extended to correlate the fracturing behavior of each coal seam to the production history. Consequently, suggestions are provided to optimize the future fracturing treatments in order to increase the production index of each well.

Formations like coal bed methane and other similar unconventionals are highly unpredictable when it comes to evaluating the accuracy of simulations carried out. This technique helps realize that each reservoir behaves differently and correlating different studies undertaken to study the particular reservoir will help engineers understand it better.

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